Different types of acoustic devices have been used through the years. One type of device is a microphone. In a microelectromechanical system (MEMS) microphone, a MEMS die includes a diagram and a back plate. The MEMS die is supported by a substrate and enclosed by a housing (e.g., a cup or cover with walls). A port may extend through the substrate (for a bottom port device) or through the top of the housing (for a top port device). In any case, sound energy traverses through the port, moves the diaphragm and creates a changing potential of the back plate, which creates an electrical signal. Microphones are deployed in various types of devices such as personal computers or cellular phones.
Microphones are used in various applications that utilize voice trigger applications. In previous approaches, an acoustic activity detector detects a voice signal and sends out a signal to wake up a digital signal processor (DSP) for the detection of key phrases in the voice. Once the key phrase is found, all input speech data can be processed. Consequently, any time that the acoustic activity detector is triggering, the DSP is constantly searching for key phrases using power. Mobile and wearable devices have small batteries that can be depleted by the repeated triggering described above.
The problems of previous approaches have resulted in some user dissatisfaction with these previous approaches.
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